Substrate positioning device, substrate positioning method and program

ABSTRACT

Noise reduction processing for detecting the circumferential edge of a wafer W placed on a rotary stage with a light-transmitting sensor, obtaining detection values provided by the light-transmitting sensor as substrate edge shape data, detecting sudden abnormal data in the substrate edge shape data, eliminating the detected sudden abnormal data and interpolating the substrate edge shape data with estimated data generated based upon surrounding data in place of the abnormal data, notch mark judgment processing for detecting a notch mark candidate in the substrate edge shape data having undergone the noise reduction processing and making a decision as to whether or not the sets of data corresponding to the notch mark candidate area satisfies a predetermined judgment condition, and substrate positioning processing for positioning the substrate based upon a notch mark that satisfies the predetermined judgment conditions are executed.

CROSS REFERENCE TO RELATED APPLICATIONS

This document claims priority to Japanese Patent Application No.2005-097006, filed Mar. 30, 2005 and U.S. Provisional Application No.60/666,708, filed Mar. 31, 2005, the entire contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a substrate positioning device, asubstrate positioning method and a program, to be adopted to position asubstrate such as a wafer based upon a notch mark detected at aperipheral edge of the substrate.

BACKGROUND OF THE INVENTION

In a substrate processing apparatus, a substrate undergoing processingfor semiconductor device production, such as a wafer, is carried into aprocessing chamber via a transfer means such as a transfer arm and aspecific type of processing, e.g., etching or film formation, isexecuted on the wafer having been carried into the processing chamber.As increasingly fine circuit patterns have come to be formed throughhighly advanced micro-processing technologies in recent years, it hasbecome necessary to position the wafer undergoing processing orinspection along the correct orientation with a high level ofpositioning accuracy in correspondence to the nano-order device designspecifications (e.g., circuit line width of 65 nm). A notch mark such asan indented notch or a linear notch, which is often referred to as anorientation flat, is formed at part of the edge of the wafer, and thewafer is positioned by using this notch mark.

The wafer is usually positioned by, for instance, disposing a lightemitting unit and a light receiving unit of a light-transmitting sensorso as to operate across the wafer edge. Light that is radiated towardthe wafer edge is transmitted through the edge, and the notch mark isthus detected as the quantity of transmitted light changes at the notchmark.

In recent years, transparent wafers constituted of optical material ortransparent material with superior light transmission characteristicsand electrical insulation characteristics, such as sapphire, glass andquartz, have become fairly common as alternatives to the conventionalsilicon wafers. However, unlike a nontransparent wafer constituted of anontransparent material such as silicon, a transparent wafer allowslight to be transmitted over substantially the entire area thereof, andit has been assumed that a notch mark at the wafer edge cannot bedetected with the light-transmitting sensor described above.

Accordingly, a light-reflecting sensor, instead of a light-transmittingsensor is used in conjunction with such a transparent wafer to detectthe notch mark by radiating light from one side of the transparent waferand receiving the light reflected from the wafer (see Japanese Laid OpenPatent Publication No. H06-085038 and Japanese Laid Open PatentPublication No. H10-163301).

A light-transmitting sensor may be utilized to detect the edge area of atransparent wafer if the wafer has a portion formed along its edge overthe entire circumference where vertical light is not allowed to advancestraight, e.g., a beveled portion formed as a slanting surface over theentire circumference.

However, since light is transmitted through almost the entire area of atransparent wafer, there is a high likelihood of the light sensorgenerating saturated data (abnormal data) due to noise light such asdisturbance light, regardless of whether the light sensor is alight-transmitting sensor or a light-reflecting sensor. For instance, ifa pattern has been formed on the transparent wafer, noise lightresulting from light diffraction manifesting at the pattern may bereceived by the light sensor and saturated data may be generated as aresult. The term “saturated data” in this context refers to dataindicating the maximum value that the light sensor is capable ofdetecting.

As described above, saturated data tend to be generated readily when thedetection target is a transparent wafer. For this reason, if wafer edgeshape data detected by the light sensor include a plurality of sets ofsaturated data indicating a noise area. A noise area may be erroneouslyjudged to be the notch mark depending upon how the saturated data aredistributed. Such an erroneous judgment leads to a problem in that thewafer positioning processing cannot be executed with accuracy.

It is to be noted that this problem may occur when the detection targetwafer is a nontransparent wafer, as well as when the target wafer is atransparent wafer. For instance, abnormal data may be generated due todisturbance light or electrical noise when the detection target wafer isa nontransparent wafer, and in such a case, a noise area may beerroneously judged to be the notch mark formed at the wafer, dependingupon the extent of variance in the abnormal data.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention, which has beencompleted by addressing the problems of the related art discussed above,it is to provide a substrate positioning device, a substrate positioningmethod and a program to be adopted to ensure that a noise area indicatedby abnormal data such as saturated data is not erroneously judged to bea notch mark formed at the circumferential edge of the substrate,thereby improving the notch mark judgment accuracy.

MEANS FOR SOLVING THE PROBLEMS

The object described above is achieved in an aspect of the presentinvention by providing a substrate positioning device that detects anotch mark formed at a circumferential edge of a substrate and positionsthe substrate based upon the detected notch mark, comprising a rotarystage on which the substrate is placed so as to be rotatable, a sensorunit that includes a light sensor capable of detecting thecircumferential edge of the substrate placed on the rotary stage and acontrol unit that obtains substrate edge shape data indicating detectionvalues provided by the light sensor of the sensor unit and positions thesubstrate based upon the substrate edge shape data thus obtained. Thecontrol unit in the substrate positioning device executes noisereduction processing for detecting sudden abnormal data in the substrateedge shape data obtained from the sensor unit, eliminating the suddenabnormal data thus detected and interpolating the substrate edge shapedata by using estimated substrate edge shape data generated based upondata from a surrounding area in place of the eliminated abnormal data,notch mark judgment processing for detecting a notch mark candidate inthe substrate edge shape data having undergone the noise reductionprocessing and making a decision as to whether or not an errormanifesting between sets of data sampled over an area corresponding tothe detected notch mark candidate and an approximate curve obtained bycurvilinearly approximating the sets of data over the area correspondingto the notch mark candidate satisfies a specific judgment condition andsubstrate positioning processing for positioning the substrate basedupon a notch mark satisfying the specific judgment condition.

The object described above is also achieved in another aspect of thepresent invention by providing a substrate positioning method fordetecting a notch mark formed at a circumferential edge of a substrateand positioning the substrate based upon the detected notch mark,comprising a data acquisition step for detecting the circumferentialedge of the substrate with a light sensor and obtaining detection valuesprovided by the light sensor as substrate edge shape data, a noisereduction step for detecting sudden abnormal data in the substrate edgeshape data, eliminating the detected sudden abnormal data andinterpolating the substrate edge shape data with estimated substrateedge shape data obtained based upon data from a surrounding area inplace of the abnormal data, a notch mark judgment step for detecting anotch mark candidate in the substrate edge shape data having undergonethe noise reduction step and making a decision as to whether or not anerror, which has been generated due to a mismatch between data sampledover an area corresponding to the notch mark candidate having beendetected and an approximate curve obtained by curvilinearlyapproximating the data over the area corresponding to the notch markcandidate, satisfies a predetermined judgment condition and a substratepositioning step for positioning the substrate based upon a notch marksatisfying the predetermined judgment condition.

By adopting the device or the method according to the present invention,sudden abnormal data (e.g., saturated data) in the substrate edge shapedata provided by the light sensor can be eliminated and thus, abnormaldata corresponding to a noise area where abnormal data that tend toreadily cause an erroneous notch mark judgment manifest repeatedly, canbe reduced. In addition, even when abnormal data are not eliminated andthe corresponding noise area is detected as a notch mark candidate, asignificant error manifests between the data of the notch mark candidateand an approximate curve obtained by curvilinearly approximating thenotch mark candidate detected over the noise area, and thus, it ispossible to disqualify the noise area as a notch mark candidate. As aresult, a noise area corresponding to abnormal data such as saturateddata is not erroneously judged to be the notch mark formed at thesubstrate edge and the notch mark judgment accuracy is improved.

In the noise reduction processing executed in the device or the method,each set of sampling data sampled at a given point and constituting thesubstrate edge shape data may be designated as target data, the targetdata may be compared with data sampled at a preceding point and asucceeding point and the sudden abnormal data may be detected by makinga decision as to whether or not the target data deviate from thepreceding data and the succeeding data by an extent equal to or greaterthan a predetermined first noise threshold value. In this case, thepredetermined first noise threshold value should assume a value selectedfrom a range over which at least three sets of data, sampled at a pointequivalent to the vertex of an area corresponding to the notch mark andat points preceding and succeeding the point corresponding to the vertexin the sampling data for the notch mark area included in the substrateedge shape data, are not eliminated.

Through such noise reduction processing, abnormal data deviating fromthe preceding and succeeding data are eliminated from the substrate edgeshape data and the substrate edge shape data are interpolated withestimated data generated based upon the preceding and succeeding data.This means that the estimated data can be obtained through calculationwith ease. In addition, while abnormal data corresponding to a noisearea that can be erroneously judged to be the notch mark are eliminated,data (e.g., data sampled at points around the vertex of the notch mark)needed in the notch mark judgment are retained and, as a result, theaccuracy of the notch mark judgment is improved.

The predetermined judgment condition based upon which the decision ismade in the notch mark judgment processing in the device or the methodmay be that in reference to the height of the notch mark candidate arearepresented by the approximate curve, the ratio of the error to theheight of the notch mark candidate area does not exceed a predeterminedfirst judgment threshold value. It is desirable that the predeterminedfirst judgment threshold value be a value selected within a range of1/40 to 7/10 of the height of the notch mark candidate area, and it iseven more desirable to select a value that is 1/10 of the height of thenotch mark candidate area. By selecting such a threshold value, it isensured that if the area corresponding to the actual notch mark isdetected as a notch mark candidate, the data are not eliminated butretained intact and that only a noise area detected as a notch markcandidate is disqualified. As a result, the notch mark judgment accuracyis improved.

In the notch mark judgment processing executed in the device or themethod, superimposed substrate edge shape data may be generated byoffsetting and superimposing data corresponding to a half cycle in thesubstrate edge shape data having undergone the noise reductionprocessing and corresponding to one cycle of the substrate, over thedata corresponding to the other half cycle, and a notch mark candidatemay be detected by using the superimposed data. In this case, a sinewavecomponent can be canceled out of the substrate edge shape data providedby the light sensor monitoring the substrate edge while the substrateplaced on the rotary stage is rotated and, as a result, the adverseeffect of decentering between the substrate center indicated in thesubstrate edge shape data and the rotational center at the rotary stagecan be eliminated.

In the notch mark judgment processing executed in the device or themethod, a prerequisite judgment condition that the number of sets ofsampling data available in correspondence to the notch mark candidate isat least equal to or greater than a predetermined number may be set, andsampling data corresponding to the notch mark candidate satisfying thisprerequisite judgment condition may be curvilinearly approximatedthrough the method of least squares. In this case, the sampling datacorresponding to the notch mark candidate are retained only when thereare a sufficient number of sets of data that enable curvilinearapproximation through the method of least squares.

The substrate undergoing the processing in the device or the method is atransparent wafer constituted of an optical material or a transparentmaterial with superior light transmittance characteristics andelectrical insulation characteristics, such as sapphire, glass orquartz. The wafer edge shape data of a transparent wafer tend to includesaturated data (abnormal data). A great advantage is achieved byadopting the present invention in conjunction with a transparent wafer,since a noise area where such saturated data are sampled is noterroneously judged to be the notch mark.

The object described above is achieved in yet another aspect of thepresent invention by providing a substrate positioning device thatdetects a notch mark formed at a circumferential edge of a substrate andpositions the substrate based upon the detected notch mark, comprising arotary stage on which the substrate is placed, a sensor unit thatincludes a light sensor capable of detecting the circumferential edge ofthe substrate placed on the rotary stage and a control unit that obtainssubstrate edge shape data indicating detection values provided by thelight sensor of the sensor unit and positions the substrate based uponthe substrate edge shape data thus obtained. The control unit in thesubstrate positioning device executes first noise reduction processingfor detecting sudden abnormal data in the substrate edge shape data,eliminating the sudden abnormal data thus detected and interpolating thesubstrate edge shape data by using estimated substrate edge shape datagenerated based upon data from a surrounding area in place of theeliminated abnormal data, second noise reduction processing forcorrecting individual sets of data, constituting the substrate edgeshape data resulting from the first noise reduction processing basedupon data sampled at surrounding areas, first judgment processing fordetecting a notch mark candidate in the substrate edge shape data havingundergone the second noise reduction processing and making a decision asto whether or not an error manifesting between sets of data sampled overan area corresponding to the detected notch mark candidate and anapproximate curve obtained by curvilinearly approximating the sets ofdata over the area corresponding to the notch mark candidate satisfies apredetermined first judgment condition, second judgment processing formaking a decision as to whether or not a coefficient in a curvilinearapproximation expression of the approximate curve obtained incorrespondence to a notch mark candidate judged to satisfy the firstjudgment condition through the first judgment processing satisfies apredetermined second judgment condition and substrate positioningprocessing for positioning the substrate based upon a notch mark judgedto satisfy the second judgment condition through the second judgmentprocessing.

The object described above is also achieved in yet another aspect of thepresent invention by providing a substrate positioning method fordetecting a notch mark formed at a circumferential edge of a substrateand positioning the substrate based upon the detected notch mark,comprising a data acquisition step for detecting the circumferentialedge of the substrate with a light sensor and obtaining detection valuesprovided by the light sensor as substrate edge shape data, a first noisereduction step for detecting sudden abnormal data in the substrate edgeshape data, eliminating the detected sudden abnormal data andinterpolating the substrate edge shape data with estimated substrateedge shape data obtained based upon data from a surrounding area inplace of the abnormal data, a second noise reduction step for correctingindividual sets of data constituting the substrate edge shape datahaving undergone the first noise reduction step based upon data sampledin surrounding areas, a first judgment step for detecting a notch markcandidate in the substrate edge shape data resulting from the secondnoise reduction step and making a decision as to whether or not an errormanifesting between sets of data sampled over an area corresponding tothe detected notch mark candidate and an approximate curve obtained bycurvilinearly approximating the sets of data over the area correspondingto the notch mark candidate satisfies a predetermined first judgmentcondition, a second judgment step for making a decision as to whether ornot a coefficient in a curvilinear approximation expression of theapproximate curve for a notch mark candidate judged to satisfy the firstjudgment condition through the first judgment step satisfies apredetermined second judgment condition and a substrate positioning stepfor positioning the substrate based upon a notch mark judged to satisfythe second judgment condition through the second judgment step.

In the device or the method according to the present invention describedabove, the first noise reduction processing is executed prior to thesecond noise reduction processing and, as a result, sudden saturateddata are eliminated through the first noise reduction processing. As aresult, data sampled over a noise area are not corrected to indicatevalues close to the values indicated over the actual notch mark throughthe second noise reduction processing. Thus, the noise area is noterroneously judged to be the notch mark formed at the wafer W in thenotch mark judgment to be detailed later.

In addition, since the first judgment processing is executed prior tothe second judgment processing, any noise area with deviant saturateddata is disqualified as a notch mark candidate through the firstjudgment with regard to the error (offset) manifesting between theapproximate curve and the notch mark sampling data. As a result, afurther improvement in the notch mark judgment accuracy is achieved.

The object described above is also achieved in yet another aspect of thepresent invention by providing a program for detecting a notch markformed at a circumferential edge of a substrate and positioning thesubstrate based upon the detected notch mark, which enables a computerto execute a data acquisition procedure for detecting thecircumferential edge of the substrate with a light sensor and obtainingdetection values provided by the light sensor as substrate edge shapedata, a noise reduction procedure for detecting sudden abnormal data inthe substrate edge shape data, eliminating the detected sudden abnormaldata and interpolating the substrate edge shape data with estimatedsubstrate edge shape data obtained based upon data from a surroundingarea in place of the eliminated abnormal data, a notch mark judgmentprocedure for detecting a notch mark candidate in the substrate edgeshape data having undergone the noise reduction procedure and making adecision as to whether or not an error manifesting between sets of datasampled over an area corresponding to the notch mark candidate havingbeen detected, and an approximate curve obtained by curvilinearlyapproximating the sets of data over the area corresponding to the notchmark candidate satisfies a predetermined judgment condition and asubstrate positioning procedure for positioning the substrate based upona notch mark satisfying the predetermined judgment condition.

The object described above is also achieved in yet another aspect of thepresent invention by providing a program for detecting a notch markformed at a circumferential edge of a substrate and positioning thesubstrate based upon the detected notch mark, which enables a computerto execute a data acquisition procedure for detecting thecircumferential edge of the substrate with a light sensor and obtainingdetection values provided by the light sensor as substrate edge shapedata, a first noise reduction procedure for detecting sudden abnormaldata in the substrate edge shape data, eliminating the detected suddenabnormal data and interpolating the substrate edge shape data withestimated substrate edge shape data obtained based upon data from asurrounding area in place of the eliminated abnormal data, a secondnoise reduction procedure for correcting individual sets of data,constituting the substrate edge shape data having undergone the firstnoise reduction procedure based upon data sampled in surrounding areas,a first judgment procedure for detecting a notch mark candidate in thesubstrate edge shape data resulting from the second noise reductionprocedure and making a decision as to whether or not an errormanifesting between sets of data sampled over an area corresponding tothe detected notch mark candidate and an approximate curve obtained bycurvilinearly approximating the sets of data over the area correspondingto the notch mark candidate satisfies a predetermined first judgmentcondition, a second judgment procedure for making a decision as towhether or not a coefficient in a curvilinear approximation expressionof the approximate curve for a notch mark candidate, judged to satisfythe first judgment condition through the first judgment procedure,satisfies a predetermined second judgment condition and a substratepositioning procedure for positioning the substrate based upon a notchmark judged to satisfy the second judgment condition through the secondjudgment procedure.

By executing either program according to the present invention describedabove, a noise area corresponding to abnormal data such as saturateddata is not erroneously judged to be the notch mark formed at thesubstrate edge and the notch mark judgment accuracy is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view presenting a structural example that may beadopted in the substrate processing apparatus achieved in an embodimentof the present invention;

FIG. 2 presents a specific example of a notch mark that may be formed ata wafer;

FIG. 3 is a schematic diagram showing a specific internal structure thatmay be adopted in the positioning device in the embodiment;

FIG. 4 illustrates the principal of the wafer edge detection executed bythe positioning device in the embodiment;

FIGS. 5A, 5B and 5C show wafer edge shape data that may be sampled inthe embodiment;

FIG. 6 presents a specific example of saturated data (abnormal data)that may be sampled in the embodiment;

FIG. 7 presents a flowchart of a specific example of the waferpositioning processing executed in the embodiment;

FIG. 8 presents a flowchart of a specific example of the noise reductionprocessing in FIG. 7;

FIG. 9 shows the first noise threshold value used in the first noisereduction processing in FIG. 8;

FIG. 10 presents a specific example of sampling data included in thewafer edge shape data;

FIG. 11 shows the results obtained by executing the first noisereduction processing on the sampling data in FIG. 10;

FIG. 12 shows the results obtained by executing the second noisereduction processing on the sampling data in FIG. 11;

FIG. 13 presents a specific example of sampling data containingsaturated data;

FIG. 14 shows the results obtained by executing only the second noisereduction processing on the sampling data in FIG. 13;

FIG. 15 presents a specific example of sampling data over a noise area,which contain a plurality of sets of saturated data;

FIG. 16 shows the results obtained by executing only the second noisereduction processing on the sampling data in FIG. 15;

FIG. 17 presents a flowchart of a specific example of the notch markdetection processing in FIG. 7;

FIG. 18 presents a specific example of sampling data corresponding to afull cycle in the wafer edge shape data;

FIG. 19 shows superimposed data generated based upon the wafer edgeshape data in FIG. 18;

FIG. 20 presents a flowchart of a specific example of the notch markjudgment processing in FIG. 17;

FIG. 21 illustrates the notch mark candidate search in FIG. 17;

FIG. 22 presents a specific example of a notch mark candidate;

FIG. 23 presents a specific example of a notch mark candidate;

FIG. 24 illustrates rise (shift) of the wave form of the superimposeddata;

FIG. 25 presents another specific example of sampling data over a noisearea, which contain a plurality of sets of saturated data;

FIG. 26 shows the results obtained by executing only the second noisereduction processing on the sampling data in FIG. 25; and

FIG. 27 is a sectional view presenting another structural example thatmay be adopted in the substrate processing apparatus in an embodiment onthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed explanation of the preferred embodiments ofthe present invention, given in reference to the attached drawings. Itis to be noted that in the specification and the drawings, the samereference numerals are assigned to components having substantiallyidentical functions and structural features to preclude the necessityfor a repeated explanation thereof.

(Structural Example for Substrate Processing Apparatus)

First, a structural example that may be adopted in the substrateprocessing apparatus in an embodiment of the present invention isexplained in reference to a drawing. The substrate processing apparatusin this example includes at least one vacuum processing unit connectedto a transfer chamber. FIG. 1 is a sectional view schematicallyillustrating the structure of the substrate processing apparatusachieved in the embodiment. The substrate processing apparatus 100includes either a single vacuum processing unit 110 or a plurality ofvacuum processing units 110 where various types of processing such asfilm formation and etching are executed on a substrate, e.g., a wafer W,in order to manufacture a semiconductor device, and a transfer unit 120that transfers the wafer W into/out of each vacuum processing unit 110.The transfer unit 120 includes a common transfer chamber 130 used totransfer wafers W.

In the example presented in FIG. 1, two vacuum processing units 110A and110B are disposed along a side surface of the transfer unit 120. Thevacuum processing units 110A and 110B respectively include processingchambers 140A and 140B and evacuatable load-lock chambers 150A and 150Bdisposed continuous to the processing chambers. In the processingchambers 140A and 140B of the vacuum processing units 110A and 110B, asingle type of processing or different types of processing can beexecuted on wafers W. Inside the processing chambers 140A and 140B,stages 142A and 142B on which wafers W can be placed are disposed. It isto be noted that the number of vacuum processing units 110, eachcomprising a processing chamber 140 and a load-lock chamber 150, is notlimited to two, and additional vacuum processing units may be disposed.

The transfer chamber 130 at the transfer unit 120 is formed as a boxwith a substantially rectangular section, where an inert gas such as N₂gas or clean air is circulated. A plurality of cassette tables 132Athrough 132C are disposed side-by-side at one of the side surfaces ofthe transfer chamber 130 ranging along the longer side of thesubstantially rectangular section. The cassette tables 132A and 132Bfunction as substrate standby ports, at which cassette containers 134Athrough 134C are placed. While FIG. 1 shows three cassette containers134A through 134C each placed on one of the cassette tables 132A through132C, the numbers of the cassette tables and cassette containers are notlimited to this example and there may be one or two cassette tables andcassette containers, or there may be four or more cassette tables andcassette containers.

At each of the cassette containers 134A through 134C, up to 25 wafers Wcan be stored in multiple racks with equal pitches. The cassettecontainers assume a sealed structure with, for instance, an N₂ gasatmosphere filling the space therein. Wafers W can be carried into/outof the transfer chamber 130 via gate valves 136A through 136C.

A common transfer mechanism (atmospheric pressure-side transfermechanism) 160 that transfers a wafer W along the length (along thedirection indicated by the arrow in FIG. 1) thereof is disposed insidethe transfer chamber 130. The common transfer mechanism 160 is fixedonto, for instance, a base 162 and the base 160 is allowed to slide on aguide rail (not shown) disposed over the central area of the transferchamber 130 so as to extend along the length thereof via, for instance,a linear motor drive mechanism. The common transfer mechanism 160 may bea double-arm mechanism equipped with two end-effectors, as shown in FIG.1, or it may be a single-arm mechanism-equipped with a singleend-effector.

At an end of the transfer chamber 130, i.e., at one side surface rangingalong the shorter side of the substantially rectangular section, apositioning device (e.g., an orienter or a pre-alignment stage) 200 isdisposed. The positioning device 200 positions (aligns) a wafer W. Thispositioning device 200 is to be described in detail later.

At the other side surface of the transfer chamber ranging along thelonger side of the substantially rectangular section, the base ends ofthe two load-lock chambers 150A and 150B are connected via switchablegate valves (atmospheric pressure-side gate valves) 152A and 152B. Thefront ends of the load-lock chambers 150A and 150B are respectivelyconnected to the processing chambers 140A and 140B via switchable gatevalves (vacuum pressure-side gate valves) 144A and 144B.

In the load-lock chambers 150A and 150B, a pair of buffer stages 154Aand 156A and a pair of buffer stages 154B and 156B on which wafers W aretemporarily held in standby are respectively disposed. In theexplanation, the buffer stages 154A and 154B disposed closer to thetransfer chamber are referred to as first buffer stages, whereas thebuffer stages 156A and 156B disposed on the other side are referred toas second buffer stages. Individual transfer mechanisms (vacuumpressure-side transfer mechanisms) 170A and 170B, each constituted withan articulated arm capable of flexing, rotating and moving up/down, aredisposed respectively between the buffer stages 154A and 156A andbetween the buffer stages 154B and 156B.

At the front ends of the individual transfer mechanisms 170A and 170B,end-effectors 172A and 172B are respectively disposed, so that wafers Wcan be transferred between the first and second buffer stages 154A and156A and between the first and second buffer stages 154B and 156B viathe end-effectors 172A and 172B respectively. It is to be noted thatwafers are carried from the load-lock chambers 150A and 150B to theprocessing chambers 140A and 140B and vice versa via the respectiveindividual transfer mechanisms 170A and 170B.

The substrate processing apparatus 100 includes a control unit 180 thatcontrols the overall operations executed in the substrate processingapparatus, including operational control for the transfer mechanisms 160and 170 and the gate valves 136, 144 and 156 as well as the positioningdevice 200. The control unit 180 includes a microcomputer constitutingthe main body of the control unit 180, a memory in which various typesof data are stored and the like.

When executing wafer processing in the substrate processing apparatusstructured as described above, a wafer W taken out of a given cassettecontainer among the cassette containers 134A through 134C by the commontransfer mechanism 160 is first carried into the positioning device 200where it is positioned (aligned). Then, the wafer W is transferred backto the common transfer mechanism 160 which carries it into the load-lockchamber 150A or 150B of the vacuum processing unit 110A or 110B where itis to undergo the processing. The wafer W is carried into the processingchamber 140A or 140B on the individual transfer mechanism 170A or 170B,and once in the processing chamber 140A or 140B, the wafer W undergoes aspecific type of processing such as etching executed by using aprocessing gas. When the processing in the processing chamber 140A or140B ends, the processed wafer W is taken back to the load-lock chamber150A or 150B by the individual transfer mechanism 170A or 170B, and thenit is carried back into the cassette container among the cassettecontainers 134A through 134C by the common transfer mechanism 160 viathe transfer chamber 130.

As increasingly fine circuit patterns have come to be formed throughhighly advanced microprocessing technologies in recent years, it hasbecome necessary to position the wafer undergoing processing orinspection along the correct orientation with a high level ofpositioning accuracy in correspondence to the nano-order device designspecifications (e.g., circuit line width of 65 nm).

Accordingly, the positioning device 200 achieved in the embodimentdetects a notch mark (e.g., a notch N constituted with a cutout, such asthat shown in FIG. 2) formed on part of the circumferential edge of thewafer W and thus accurately detects the orientation of the wafer Wthrough the wafer positioning processing to be detailed later. As aresult, the orientation of the wafer W can be adjusted accurately alonga specific direction.

(Structural Example for Positioning Device)

A specific structural example that may be adopted in the positioningdevice is now explained in reference to drawings. FIG. 3 schematicallyillustrates an example of an internal structure that may be adopted inthe positioning device 200. FIG. 4 illustrates the principal of thewafer edge detection executed by the positioning device 200. Thepositioning device 200 is constituted by disposing inside asubstantially cylindrical container a rotary stage 210 on which thewafer W is placed and a sensor unit 220 that detects the circumferentialedge of the wafer W with a light-transmitting sensor 250.

The rotary stage 210 may include, for instance, a drive unit 212, arotating drive shaft 214 extending from the drive unit 212 and a rotaryplate 216 fixed onto the rotating drive shaft 214, on which the wafer Wis placed. The rotary plate 216 is allowed to move up/down freely and isalso made to rotate by a specific extent by a motive force transmittedby the drive unit 212 via the rotating drive shaft 214. The rotary stage210 is connected to the control unit 180 and its drive is controlled inresponse to a control signal provided by the control unit 180.

It is to be noted that while the outer diameter of the rotary plate 216is set smaller than the outer diameter of the wafer W, the rotary plate216 should still be large enough to fully support the wafer W as itrotates. In addition, a rubber pad or an electrostatic holding pad (notshown) is disposed at the upper surface of the rotary plate 216 so thatthe wafer W placed on the rotary plate 216 is held fast against thecentrifugal force while the rotary plate 216 rotates.

The sensor unit 220 includes a light-transmitting sensor 250,representing an example of a detection means for detecting thecircumferential edge of the wafer W. The light-transmitting sensor 250includes a light emitting unit 230 and a light receiving unit 240, whichare disposed so as to operate across the circumferential edge of thewafer W set on the rotary stage 210. More specifically, the lightemitting unit 230 may be disposed so that it assumes a position underthe wafer W and the light receiving unit 240 may be disposed so that itassumes a position above the wafer W.

It is to be noted that the light emitting unit 230 and the lightreceiving unit 240 of the light-transmitting sensor 250 are individuallyconnected to the control unit 180 so that the light emitting unit 230 iscontrolled based upon a control signal provided by the control unit 180and a signal from the light receiving unit 240 is transmitted to thecontrol unit 180. In addition, the sensor unit 220 is allowed to movereciprocally along the radius of the wafer W by a sensor unit drive unit(not shown). The sensor unit drive unit is connected to the control unit180 and its drive is controlled in response to a control signal providedby the control unit 180.

The light emitting unit 230 includes a light emitting element 232 suchas a light emitting diode and a lens 234, as shown in FIG. 4. It is tobe noted that a slit (not shown) may be formed above the lens 234 in thelight emitting unit 230 to improve the rectilinear propagationcharacteristics of light by reducing the adverse effect of disturbancelight on the transmitted light received at the light receiving unit 240.The light receiving unit 240 is constituted with an image-capturingelement such as a CCD (charge coupled device) sensor. Alternatively, thelight receiving unit may be constituted with a photo sensor element suchas a photodiode.

Light emitted from the light emitting element 232 at the light emittingunit 230 of the sensor unit 220 structured as described above isreceived at the light receiving element of the light receiving unit 240via the lens 234, and is converted to a position signal. The positionsignal resulting from the conversion is then transmitted to the controlunit 180. The signal transmitted to the control unit 180 is used inpositioning processing and the like executed for the wafer W by thecontrol unit 180. Based upon position information with regard to thewafer W, obtained through the wafer positioning processing, the controlunit 180 controls the rotary stage 210 via the drive unit 212 and alsocontrols the common transfer mechanism 160 to position (align) the waferW. It is to be noted that the positioning processing executed for thewafer W is to be described in detail later.

As a wafer W is placed on the rotary plate 216 of the rotary stage 210via, for instance, the common transfer mechanism 160, the wafer W iselectrostatically held onto the rotary plate 216 in the positioningdevice 200. Then, while the wafer W rotates together with the rotaryplate 216, light is radiated from the light emitting unit 230 andtransmitted light is received at the light receiving unit 240. Thesignal over an area where the wafer W is not present indicates an ONlevel, whereas the signal over the area where the circumferential edgeof the wafer W is present, blocking the optical path between the lightemitting unit 230 and the light receiving unit 240 indicates an OFFlevel, thereby enabling detection of the circumferential edge of thewafer W. By detecting the position of the edge of the wafer W while thewafer W rotates one full cycle, wafer edge shape data, which constituteinformation related to the shape of the wafer W at its edge, can becollected.

(Wafer Edge Shape Data)

In reference to a drawing, the wafer edge shape data are explained. FIG.5 shows wafer edge shape data, with FIG. 5A presenting a graph of waferedge shape data sampled when the center of the wafer W and therotational center at the rotary stage 210 are aligned and FIG. 5Bpresenting a graph of wafer edge shape data sampled when the center ofthe wafer W and the rotational center at the rotary stage are notaligned. FIG. 5C presents a graph obtained by offsetting andsuperimposing the data corresponding to half a cycle in the graph inFIG. 5B over the data corresponding to the other half cycle.

Since the shape at the edge of the substantially circular wafer remainsconstant, the wafer edge shape data are represented by a substantiallyhorizontal straight line indicated by the solid line A in FIG. 5A exceptfor the area B corresponding to the notch mark, as long as the center ofthe wafer W and the rotational center of the rotary stage 210 arealigned.

However, it is difficult to accurately align the center of the wafer W,which is set on the rotary stage 210 via the common transfer mechanism160, with the rotational center at the rotary stage 210. For thisreason, the center of the wafer W and the rotational center of therotary stage 210 are offset from each other and thus, the actual waferedge shape data are represented by a substantially sinusoidal curve, asindicated by the solid line A′ in FIG. 5B except for the area B′corresponding to the notch mark.

Accordingly, in order to accurately detect the notch mark at the wafer Wbased upon the wafer edge shape data shown in FIG. 5B, superimposed dataare generated by offsetting the wafer edge shape data corresponding tohalf a cycle (180°) in the wafer edge shape data sampled over a fullcycle, i.e., wafer edge shape data sampled while the wafer W rotatesonce (360°), such as those shown in FIG. 5B, and superimposing the halfcycle wafer edge shape data over the wafer edge shape data correspondingto the other half cycle. Such superimposed wafer edge shape data arerepresented by a substantially horizontal straight line, as indicated bythe solid line A″ in FIG. 5C except for the area B″ corresponding to thenotch mark. Since the sinewave component is canceled out in thesesuperimposed wafer edge shape data, the adverse effect of the offsetbetween the center of the wafer W and the rotational center of therotary stage 210 on the wafer edge shape data is eliminated to allowaccurate detection of the notch mark (area B) at the wafer W.

(Nontransparent Wafer and Transparent Wafer)

Now, the wafer W to be positioned by the positioning device 200 achievedin the embodiment is explained. The wafer W, positioned by thepositioning device 200 achieved in the embodiment may be anontransparent wafer W constituted of a nontransparent material such assilicon, or it may be a transparent wafer W constituted of an opticalmaterial or a transparent material with desirable light transmissioncharacteristics and electrical insulation characteristics, such assapphire (aluminum oxide single crystal substrate), glass or quartz(SiO₂). Namely, the transparent wafer W positioned by the positioningdevice achieved in the embodiment may be a sapphire substrate, a glasssubstrate, a quartz wafer or an SOS (silicon-on-sapphire) substrate.

The sapphire substrate may be used when manufacturing, for instance, anLCD backlight surface light emitting LED or the like, a glass substratemay be used when manufacturing, for instance, an infrared cut-off filter(IR cut-off filter) or the like, and a quartz wafer may be used for, forinstance, MEMS (micro electromechanical system). It is to be noted thatan SOS substrate is a composite substrate constituted with silicon andsapphire.

When the target wafer to be positioned by the positioning device 200 isa nontransparent wafer W, the light from the light emitting unit 230 istransmitted through an area where the nontransparent wafer W is notpresent but is not transmitted through an area over which thenontransparent wafer W is present. Thus, the edge of the wafer W at theboundary of these areas can be detected with ease. In contrast, when thetarget wafer to be positioned by the positioning device 200 is atransparent wafer W, light is transmitted over most of the areas wherethe transparent wafer W is present as well as through the area where thetransparent wafer W is not present and, for this reason, detection ofthe circumferential edge of the transparent wafer W is considered to bemore difficult than the detection of the circumferential edge of thenontransparent wafer W.

However, even when the positioning target is a transparent wafer W suchas that described above, the edge of the transparent wafer W can bedetected by using the light-transmitting sensor 250 to detect an area(e.g., a beveled area) formed along the edge of the wafer W over itsentire circumference which does not allow beams traveling perpendicularto the wafer to advance straight.

For instance, at a beveled portion F formed as a slanted surface alongthe edge of the wafer W over its entire circumference, as shown in FIG.4, the light from the light emitting unit 230 is reflected and thesignal received at the light receiving unit 240 over the range where thebeveled portion F is formed indicates an OFF level. Accordingly, theedge of the transparent wafer W is detected in the embodiment bydetecting the beveled portion F of the wafer W. Consequently, thecircumferential edge of the transparent wafer W can be detected just aseasily as the circumferential edge of the nontransparent wafer W.

FIG. 4 presents a graph of the waveform indicating the quantity of lightreceived at the light receiving unit 240 when the light from the lightemitting unit 230 is radiated onto the circumferential edge of thetransparent wafer W. The horizontal axis of the graph in FIG. 4indicates the position of the sensor unit 220 along the scanningdirection, whereas the quantity of light received at the light receivingunit 240 is indicated along the vertical axis. The received lightquantity level enters an ON state if light is transmitted, whereas itenters an OFF state if no light is transmitted.

As shown in FIG. 4, light from the light emitting unit 230 istransmitted through most of the area where the transparent wafer W ispresent, as well as through the area where the transparent wafer W isnot present and thus, the quantity of light received at the lightreceiving unit 240 mostly indicates an ON level. However, the quantityof light received at the light receiving unit 240 in correspondence tothe area where the beveled portion F is formed at the transparent waferW indicates an OFF level, as shown in FIG. 4. Accordingly, the areawhere the quantity of light received at the light receiving unit 240indicates an OFF level over a predetermined range can be judged to bethe beveled portion F of the transparent wafer W and the position atwhich this area is present can be detected as the circumferential edgeof the transparent wafer W.

As a result, the circumferential edge of the transparent wafer W can bedetected just as easily as the circumferential edge of thenontransparent wafer W, which allows the positioning device 200 toposition the transparent wafer W equally effectively by adopting thestructure for positioning the nontransparent wafer W. In other words,the positioning device 200 is able to position both the transparentwafer W and the nontransparent wafer W equally effectively.

The wafer edge shape data are obtained by detecting the wafercircumferential edge in correspondence to a single rotation (singlecycle) of the wafer with the sensor unit 220 while the wafer W placed onthe rotary stage 210 is rotated.

However, since the transparent wafer W ranges over a narrow area alongthe radio direction at the beveled portion F, it is more readilyaffected by disturbance light, compared to the nontransparent wafer W.For instance, if a pattern is formed on the transparent wafer W, thelight receiving unit 240 may receive noise light attributable to a lightdiffraction phenomenon or the like occurring at the pattern.

Thus, if noise light is received within the range of the beveled portionF while detecting part of the circumferential edge of the transparentwafer W and the signal over the range indicates an ON level, the wafercircumferential edge over this area cannot be detected. Namely, whilethe sensor unit 220 is scanned further toward the center of the wafer W,the sensor unit 220 moves past the beveled portion F of the transparentwafer W and thus, the edge of the wafer W over this area cannot bedetected. Under such circumstances, the wafer edge shape data areprovided as saturated data (abnormal data) indicating an ON level.

Saturated data in this case indicates the maximum value of the quantityof light that can be detected by the light receiving unit 240. Forinstance, assuming that the light receiving unit 240 is constituted witha CCD sensor and that the received light quantity is indicated by thenumber of pixels, the saturated data indicate the maximum number ofpixels at which light can be detected at the CCD sensor. The valueindicated by the saturated data is a value provided when no detectionpoint is detected within the detection range of, for instance, a CCDsensor. FIG. 6 presents a specific example of such saturation data(abnormal data). FIG. 6 shows part of the wafer edge shape data, withthe number of sampling points (equivalent to the wafer rotationalangles) indicated along the horizontal axis and the wafer edge shapedata indicated along the vertical axis. The sampling data over an area Ain FIG. 6 are represented by a substantially straight line, indicatingthe shape of the wafer circumferential edge. The data over an area C, onthe other hand, indicate a noise area where saturated data indicating asaturation level manifests. Over the area C, sudden saturated datamanifest repeatedly. In other words, the data fluctuate between thelevel at the area A and the saturation level almost continuously.

If a plurality of sets of saturated data manifest as a noise area inpart of the wafer edge shape data corresponding to one rotation of thewafer (one cycle), the noise area (e.g., the area C in FIG. 6) may beerroneously judged to be a notch mark formed at the wafer W, dependingupon the manner with which the saturated data are distributed (e.g.,sudden saturated data manifesting repeatedly as in the area C in FIG.6). Such an erroneous judgment disallows accurate execution of waferpositioning processing.

Accordingly, the positioning processing executed for the wafer Waccording to the present invention includes noise reduction processingthrough which any sudden saturated data (abnormal data) are eliminatedas noise and notch mark judgment processing executed unaffected bysaturated data (abnormal data). The positioning processing for the waferW can thus be executed accurately without being affected by saturateddata (abnormal data) that may manifest when positioning a transparentwafer W.

(Wafer Positioning Processing)

Next, a specific example of the wafer positioning processing executed byengaging the positioning device 200 described above is explained inreference to the drawing. FIG. 7 presents a flowchart of the specificexample of the wafer positioning processing. In the embodiment, thepositioning processing for the wafer W is executed by the control unit180 by reading out and executing program data.

The positioning processing for the wafer W is executed as shown in FIG.7 by first obtaining the wafer edge shape data in step S100 in theembodiment. More specifically, while the wafer W placed on the rotarystage 210 is rotated, sampling data (e.g., wafer edge shape data such asthose shown in FIG. 6) sampled at the wafer edge by radiating light ontothe wafer edge and receiving the transmitted light while the wafer onthe rotating stage 210 rotates one full cycle, are received at thesensor unit 220. The sampling data are then stored into an actual datastorage area at a storage means constituted with a memory in, forinstance, the control unit 180.

(Noise Reduction Processing)

Next, in step S200, noise reduction processing is executed to reducenoise contained in the wafer edge shape data having been sampled by thesensor unit 220. FIG. 8 presents a flowchart of a specific example ofthe noise reduction processing. As shown in FIG. 8, the noise reductionprocessing in the embodiment includes two stages of processing, i.e.,first noise reduction processing (step S210) and second noise reductionprocessing (step S220) following the first noise reduction processing.

First, the first noise reduction processing is described. Through thefirst noise reduction processing, sudden abnormal data such as saturateddata are eliminated as noise and the wafer edge shape data areinterpolated with estimated wafer edge shape data generated based uponthe sampling data sampled at the surrounding points in place of theeliminated abnormal data. For instance, the first noise reductionprocessing may be executed on the actual wafer edge shape data, and thedata having undergone the processing may be stored as processing datainto a processing data processing area in the control unit 180. In thiscase, sudden abnormal data are not allowed to adversely affect thejudgment made with regard to the notch mark at the wafer W.

The first noise reduction processing may be executed as follows. First,sudden abnormal data in the wafer edge shape data are detected. Morespecifically, a decision is made as to whether or not each set ofsampling data in the wafer edge shape data, sampled at a given point, issudden abnormal data. Namely, a given set of data designated as thejudgment target is compared with data sampled at a preceding samplingpoint and the data sampled at the following sampling point and adecision is made as to whether or not the target data deviate from thepreceding and succeeding data by an extent equal to or greater than afirst noise threshold value (first noise judgment condition).

This first noise judgment condition may be expressed as in (1-1) and(1-2) below in which t_(a) represents the target data, t_(a−1)represents the data immediately preceding the target data t_(a), t_(a+1)represents the data immediately succeeding the target data t_(a) and m₁represents the first noise threshold value.t _(a) −t _(a−1) >m ₁  (1-1)t _(a) −t _(a+1) >m ₁  (1-2)

The decision with regard to the first noise judgment condition may bemade by storing the target data t_(a), the immediately preceding datat_(a−1) and the immediately succeeding data t_(a+1) in the wafer edgeshape data in the actual data storage area respectively into a targetdata storage area, an immediately preceding data storage area and animmediately succeeding data storage area at a storage means constitutedwith a memory or the like at the control unit 180 and comparing thesedata.

If the target data t_(a) satisfy both expressions (1-1) and (1-2), thetarget data t_(a) are judged to be sudden abnormal data. If, on theother hand, the target data do not satisfy both expressions (1-1) and(1-2), i.e., if the target data satisfy neither expression (1-1) or(1-2), or if the target data satisfy only either (1-1) or (1-2), thetarget data t_(a) are judged not to be sudden abnormal data.

If the target data t_(a) are judged not to be sudden abnormal data, thetarget data t_(a) are not eliminated. In such a case, the target datat_(a) are retained as processing data in the processing data processingarea.

If, on the other hand, the target data t_(a) are judged to be suddenabnormal data, the target data t_(a) are eliminated. Then, the averageof the values indicated by the immediately preceding data t_(a−1) andthe immediately succeeding data t_(a+1) is calculated to be used asestimated data t_(a)′, and the estimated data t_(a)′ are used tointerpolate the wafer edge shape data in place of the eliminated targetdata t_(a). Accordingly, the estimated data t_(a)′ instead of the targetdata t_(a) are stored as processing data in the processing dataprocessing area.

Sudden abnormal data cannot be eliminated if too large a value isselected for the first noise threshold value m₁. However, if the firstnoise threshold value m₁ assumes a value that is excessively small, datacorresponding to the vertex of the notch mark may be erroneously judgedto be sudden abnormal data and be eliminated. If the data correspondingto the vertex of the notch mark are eliminated, accurate notch markjudgment may be impossible. Accordingly, a value that will not allow theelimination of data corresponding to, at least, points near the vertexof the notch mark should be selected for the first noise threshold valuem₁.

A specific method that may be adopted when determining such a firstnoise threshold value m₁ is now explained. In the embodiment, the firstnoise threshold value m₁ is determined within a range over which thedata corresponding to the vertex of the notch mark, at least, are noteliminated based upon the sampling data sampled in the areacorresponding to the notch mark in the wafer edge shape data. Morespecifically, the first noise threshold value m₁ assumes a valueselected from a range over which at least the data sampled at threesampling points, i.e., at the sampling point corresponding to the vertexof the notch mark, the immediately preceding sampling point and theimmediately succeeding sampling point, in the sampling datacorresponding to the notch mark area are not eliminated.

However, the sampling data sampled over the area corresponding to thenotch mark indicate values that are fairly deviant relative to oneanother. For this reason, it is more desirable to set the first noisethreshold value m₁ in a range over which the data sampled at fivesampling points, i.e., at the sampling point corresponding to the vertexof the notch mark area, the two preceding sampling points and the twosucceeding sampling points, in the sampling data sampled over the areacorresponding to the notch mark are not eliminated, in order to ensurethat the data sampled at the point corresponding to the vertex of thenotch mark are not eliminated with greater reliability.

In reference to FIG. 9 presenting a specific example of sampling datasampled over the area corresponding to the notch mark at the wafer W,the first noise threshold value m₁ is explained in further detail. Thenumber of sampling points is indicated along the horizontal axis and thevalues indicated by the wafer edge shape data sampled at the individualsampling points, i.e., the numbers of pixels at the CCD sensorconstituting the light receiving unit 240, are indicated along thevertical axis in FIG. 9. It is to be noted that the count valueindicating the quantity of light received at the light receiving unit240 may instead be indicated along the vertical axis. It is to be notedthat the number of sampling points and the values indicated in the waferedge shape data are also respectively indicated along the horizontalaxis and the vertical axis in FIGS. 10 through 16 and FIGS. 22 through26 in reference to which an explanation is to be given later. Instead ofthe number of pixels at the CCD sensor or the count value indicating thequantity of light received at the light receiving unit 240, the dataobtained by converting the number of pixels at the CCD sensor or thecount value indicating the received light quantity to a value indicatingthe distance (mm) between a reference position and the wafer edgeinstead may be used as the wafer edge shape data.

Using sampling data t₁₁ to t₁₇ sampled over the area corresponding tothe notch mark at the wafer W shown in FIG. 9, the differences betweenthe data t₁₄ sampled at the vertex sampling point corresponding to thevertex of the notch mark and the data t₁₂ sampled at the (vertex−2)sampling point and between the data t₁₄ and the data t₁₆ sampled at the(vertex+2) sampling point are calculated. Then, the value indicating agreater difference is selected for the first noise threshold value m₁.The first noise threshold value m₁ thus determined is pre-stored into afirst noise threshold value storage area at the storage meansconstituted with the memory or the like at the control unit 180.

Through the first noise reduction processing executed as described abovein the embodiment, abnormal data sampled at a given sampling point andindicating a markedly deviant value are eliminated and the wafer edgeshape data are interpolated by using estimated data generated based uponsurrounding data such as preceding and succeeding data. As a result, theabnormal data in a noise area where abnormal data manifest repeatedly toreadily cause erroneous notch mark judgment are eliminated and such anoise area is no longer allowed to adversely affect the notch markjudgment. In addition, in the first noise reduction processing executedin the embodiment, data needed in the notch mark judgment, i.e., thedata sampled over the area around the vertex of the notch mark, are noteliminated and are, therefore, retained.

For instance, assuming that the wafer edge shape data include samplingdata t₂₁ through t₃₃ indicated by “X” in FIG. 10, the data t₂₇ and t₃₁deviating from the surrounding data by extents equal to or greater thanthe first noise threshold value m₁ are judged to be abnormal data andare eliminated accordingly, whereas the data t₂₃ deviating by an extentless than the first noise threshold value m₁ are not judged to beabnormal data and are retained. Accordingly, the wafer edge shape datahaving undergone the first noise reduction processing are interpolatedwith estimated data indicated by “O” in FIG. 11 replacing the data t₂₇and t₃₁ having been judged to be abnormal data, whereas the data t₂₃having been judged not to be abnormal data are retained, as shown inFIG. 11.

In the first noise reduction processing, abnormal data sampled at agiven sampling point and indicating a markedly deviant value areeliminated but abnormal data sampled at successive sampling points areretained. Only data with a markedly deviant value sampled at a givenpoint are eliminated in order to simplify the calculation of estimateddata to be used in the data interpolation. It is to be noted that anyabnormal data sampled at successive sampling points that are retained inthe wafer edge shape data do not present a problem since they aredisqualified as a notch mark candidate through the notch mark judgmentprocessing to be detailed later.

Next, the second noise reduction processing is explained. In the secondnoise reduction processing, noise data which are offset relative to thesurrounding sampling data are corrected based upon the surroundingsampling data. As a result, the extent of deviance in the wafer edgeshape data due to noise is reduced and thus, the noise does notadversely affect the notch mark judgment for the wafer W. It is to benoted that the second noise reduction processing is executed on thewafer edge shape processing data resulting from the first noisereduction processing.

The second noise reduction processing may be executed as follows. First,all the sets of wafer edge shape processing data are sequentiallycorrected, one set at a time. More specifically, data sampled at aspecific sampling point are designated as target data, the largest datavalue and the smallest data value among the values indicated by thetarget data and the data sampled at the two preceding sampling pointsand the two succeeding sampling points are subtracted from the sum ofthe values indicated by the data sampled at the five sampling points andthe value obtained by dividing the subtraction results by 3 is used ascorrection data. Then, the target data are replaced with the correctiondata.

Through the second noise reduction processing executed as describedabove in the embodiment, data indicating a lower value deviating fromthe surrounding sampling data as well as data indicating a higher valuedeviating from the surrounding sampling data are corrected. Dataobtained by executing the second noise reduction processing on thesampling data in FIG. 11 having undergone the first noise reductionprocessing may be as shown in FIG. 12. FIG. 12 indicates that the datat₂₃ that have not been eliminated through the first noise reductionprocessing are corrected based upon the surrounding data, i.e., replacedwith the correction data indicated by “□”. It is to be noted that thedata indicated by “X” and “O” in FIG. 12 already indicate valuesconsistent with those of the surrounding data and thus, the data remainunchanged even when they are replaced with the correction data.

In addition, by executing the second noise reduction processing afterthe first noise reduction processing, the likelihood of correctingsaturated data (abnormal data remaining after the first noise reductionprocessing so as to reduce noise through the second noise reductionprocessing is raised. For instance, assuming that the wafer edge shapedata initially contained a plurality of (5) sets of saturated data(abnormal data) and that a single set of saturated data among thesesaturated data remain after the first noise reduction processing, theretained saturated data can be corrected through the second noisereduction processing so as to reduce noise.

It is to be noted that while an explanation is given above in referenceto the embodiment on an example in which the noise reduction processingis executed over two stages, i.e., the first noise reduction processingand the second noise reduction processing, the present invention is notlimited to this example and the first noise reduction processing alonemay be executed as the noise reduction processing. Namely, suddenabnormal data can be eliminated simply by executing the first noisereduction processing and thus, saturated data that may manifest readilywhen data are sampled from a transparent wafer can be effectivelyeliminated. However, by executing the first noise reduction processingand the second noise reduction processing in combination as in theembodiment, abnormal data can be eliminated to a greater extent thanthrough the first noise reduction processing alone. As a result, noiseattributable to abnormal data such as saturated data that may adverselyaffect the notch mark judgment for the wafer W can be more effectivelyreduced.

In addition, the second noise reduction processing alone may be executedas the noise reduction processing in conjunction with a nontransparentwafer, since problems attributable to saturated data which readilymanifest when data are sampled from a transparent wafer, as describedlater, are not a concern. In the case of a transparent wafer however, aplurality of sets of saturated data are likely to manifest and, for thisreason, if the second noise reduction processing alone is executed asthe noise reduction processing on the actual wafer edge shape data, thesaturated data may adversely affect the correction data calculatedthrough the second noise reduction processing.

For instance, let us consider data generated by executing the secondnoise reduction processing alone on sampling data containing saturateddata such as those shown in FIG. 13. As long as only one set ofsaturated data is included in five sets of sampling data sampled at fivesuccessive sampling points (e.g., when the data are t₂₃, t₂₇ or t₃₁) thediscrete saturated data are corrected to indicate the value matching thevalue of the surrounding data, as shown in FIG. 14, and thus, no problemoccurs. If, on the other hand, two sets of saturated data are includedin five sets of sampling data sampled at five successive sampling points(e.g., when the data t₂₉ are the target data), the value obtained bysubtracting the largest data value and the smallest data value from thesum of the values indicated at the five successive sampling points willcontain the value indicated by the saturated data sampled at onesampling point. As a result, the correction data for the target data t₂₉will be affected by the retained saturated data, increasing the valueindicated by the corrected data as shown in FIG. 14. This means that ifthe second noise reduction processing alone is executed, normal data maybecome erroneously corrected to increase noise while, at the same time,abnormal data are corrected so as to reduce noise.

Thus, depending upon how saturated data are distributed (e.g., suddensaturated data repeatedly manifesting as in the area C in FIG. 6), thedata over the noise area may be corrected to indicate values close tothose indicated by the data corresponding to the notch mark through thesecond noise reduction processing. For instance, if the second noisereduction processing alone is executed on sampling data sampled over anoise area and containing a plurality of sets of saturated data, asshown in FIG. 15, the corrected data over the noise area may becomesimilar to those corresponding to the notch mark, as shown in FIG. 16.In such a case, the noise area may be erroneously judged to be the notchmark at the wafer W.

Accordingly, it is particularly desirable to execute the first noisereduction processing prior to the second noise reduction processing inconjunction with a transparent wafer W. Since sudden saturated data areeliminated through the first noise reduction processing, the extent towhich the second noise reduction processing is affected by saturateddata can be minimized. In other words, since no noise area is allowed tobe corrected through the second noise reduction processing to becomedata similar to those of the notch mark, a noise area is not erroneouslyjudged to be the notch mark at the wafer W in the notch mark judgment tobe explained later. As a result, the notch mark judgment accuracy isimproved.

It is to be noted that similar problems to those inherent to atransparent wafer W may also occur with regard to a nontransparent waferW, if abnormal data attributable to electrical noise or the likeoccurring in, for instance, the signal control manifest. For thisreason, the first noise reduction processing may be executed prior tothe second noise reduction processing in conjunction with anontransparent wafer W as well. In short, the same noise reductionprocessing may be executed regardless of the wafer type, i.e., whetherdata are being sampled from a transparent wafer W or a nontransparentwafer W.

(Notch Mark Detection Processing)

Once the noise reduction processing described above ends, the operationreturns to the main routine in FIG. 7 in which notch mark detectionprocessing is executed in step S300. The notch mark detection processingis executed on the wafer edge shape data (processing data) havingundergone the noise reduction processing. FIG. 17 shows a specificexample of the notch mark detection processing.

In step S310 in FIG. 17, superimposed data are prepared. Morespecifically, sampling data corresponding to half a cycle (180°) in thewafer edge shape data are offset and superimposed over the sampling datataken over the other half cycle. For instance, by offsetting andsuperimposing sampling data taken over half a cycle (180°) in the waferedge shape data in FIG. 18 over the sampling data taken over the otherhalf cycle, the superimposed data shown in FIG. 19 are obtained. FIGS.18 and 19 represent an example in which sampling data are taken at 3000sampling points in correspondence to a single rotation of the wafer.Accordingly, the values 0 through 3000 taken along the horizontaldirection correspond to rotational angles 0° through 360° of the waferW.

Next, a decision is made with regard to the ratio of the number of setsof valid data in step S320. The term “valid data” in this context refersto data within a range over which data can be detected by the sensorunit 220 along the radial direction of the wafer, and data outside thedetectable range are determined to be invalid. For instance, if thecenter of the wafer W and the rotational center at the rotary stage 210are offset from each other to a significant extent, the wafercircumferential edge may not be entirely contained in the detectablerange over which the wafer edge can be detected along the radialdirection by the sensor unit 220. As a result, the sensor unit may notbe able to detect the wafer edge and the wafer edge shape data maycontain successive sets of invalid data (may be saturated data in thecase of a transparent wafer W through which the light from thelight-transmitting sensor 250 is transmitted). If the ratio of thenumber of sets of valid data to the total number of sets of wafer edgeshape data having been sampled is low, the wafer edge shape cannot beaccurately detected and ultimately, the notch mark judgment cannot beexecuted accurately for the wafer W. For this reason, the ratio of thenumber of valid data to all the total number of sets of wafer edge shapedata having been sampled is determined.

Next, a decision is made in step S330 as to whether or not the number ofsets of valid data is less than a predetermined value. Morespecifically, a decision may be made, for instance, as to whether or notthe number of sets of valid data is less than 3/10 of the sets ofsampling data sampled while the wafer rotates once (360°) in the waferedge shape data. This decision may be made by using superimposed datasuch as those shown in FIG. 19 and making a decision as to whether ornot the number of sets of valid data is less than ⅗ of the number ofsets of sampling data sampled over a half rotation (180°). It is to benoted that the criterion to be adopted in the valid data judgment is notlimited to that described above, and any numerical value may be set incorrespondence to the required level of accuracy.

If it is decided in step S330 that the number of sets of valid data isless than the predetermined value, error processing is executed in stepS370. In the error processing, a message indicating that effectivealignment processing cannot be executed is displayed at a display meanssuch as a display unit and the wafer W is repositioned on the rotarystage 210 via the common transfer mechanism 160.

If it is decided in step S330 that the number of sets of valid data isequal to or greater than the predetermined value, the average valueamong the values indicated by the superimposed data obtained from thewafer edge shape data and a standard deviation (δ) of the superimposeddata are calculated. The average value and the standard deviation (δ)may be calculated by excluding data over a specific range (the areacorresponding to the notch mark) containing the position, at which thepeak value (the largest value) has been sampled, from the valid data. Bycalculating the average value and the standard deviation (δ) without thedata over the area corresponding to the notch mark and the invalid data,highly accurate average value and standard deviation (δ) can beobtained. It is to be noted that the average value and the standarddeviation (δ) of the superimposed data obtained from the wafer edgeshape data, having been calculated as described above, are stored intothe memory or the like at the control unit 180.

(Notch Mark Judgment Processing)

Next, notch mark judgment processing is executed in step S350. FIG. 20,presents a flowchart of a specific example of the notch mark judgmentprocessing. As shown in FIG. 20, the notch mark judgment processing isexecuted by first searching for a notch mark candidate in thesuperimposed data generated based upon the wafer edge shape data in stepS351.

More specifically, a notch mark candidate is searched based upon theaverage value and the standard deviation (δ) of the superimposed datagenerated based upon the wafer edge shape data as described earlier. Forinstance, the sum of the average value of the superimposed data and 4δmay be designated as a threshold value, data with a value exceeding thethreshold value may be searched for in the superimposed data and suchdata may be judged to represent a notch mark candidate, as shown in FIG.21.

Next, in step S352, a decision is made as to whether or not a notch markcandidate has been detected through the search. If it is decided that nonotch mark candidate has been detected through the search, errorprocessing is executed in step S359. In the error processing, a messageindicating that effective alignment processing cannot be executed isdisplayed at the display means such as display unit, and the wafer W isrepositioned on the rotary stage 210 via the common transfer mechanism160.

If it is decided in step S352 that a notch mark candidate has beendetected through the search, prerequisite judgment processing isexecuted in step S353 on the sampling data corresponding to the detectednotch mark candidate. The decision with regard to a prerequisitejudgment condition is made in this embodiment so as to ensure that thesubsequent main judgment (e.g., first judgment processing and secondjudgment processing) for the notch mark candidate can be executedaccurately.

The prerequisite judgment condition may be that the number of sets ofsampling data corresponding to the notch mark candidate be equal to orgreater than a predetermined value (e.g., 3), since the sampling datacannot be curvilinearly approximated in the main judgment (e.g., thefirst judgment processing and the second judgment processing) unlessthere are at least three sets of sampling data corresponding to thenotch mark candidate.

Another prerequisite judgment condition that may be considered is thatthe number of sets of saturated data contained in the sampling datacorresponding to the notch mark candidate is less than a predeterminedvalue (e.g., 20), so as not to execute the first judgment processing(step S355) or the second judgment processing (step S357), if there are20 or more sets of saturated data contained in the sampling datacorresponding to the notch mark candidate and thus the notch markcandidate is highly likely to be a noise area. Through such prerequisitejudgment processing, an erroneous notch mark judgment attributable tosaturated data is preempted.

Yet another prerequisite judgment condition that may be considered isthat the number of sets of sampling data corresponding to the notch markcandidate is within an allowable range (e.g., a reference value 9±4 ifthe notch mark is constituted with a notch) within which the samplingdata can conceivably represent the notch mark. FIG. 22 presents aspecific example of a notch mark candidate that may be detected when thenotch mark is formed with a notch. When the notch mark is constituted asa notch, a specific notch width is indicated by the sampling datacorresponding to a notch mark candidate, the number of sets of which iswithin the allowable range, and such a notch mark candidate is highlylikely to be the actual notch mark.

It is to be noted that the prerequisite judgment processing may beexecuted based upon any one of the prerequisite judgment conditionsdescribed above or it may be executed by using any two of theprerequisite judgment conditions in combination. However, it is mostdesirable to execute the prerequisite judgment processing based upon allthe prerequisite judgment conditions described above in order to executethe subsequent notch mark main judgment with higher accuracy.

In step S354, a decision is made as to whether or not the sampling datacorresponding to the detected notch mark candidate satisfy theprerequisite judgment conditions described above. If it is decided instep S354 that the sampling data do not satisfy the prerequisitejudgment conditions, the operation returns to step S351 to search foranother notch mark candidate. If no other notch mark candidate isdetected, error processing is executed, whereas if another notch markcandidate is detected through the search, the prerequisite judgmentprocessing is executed again for the new notch mark candidate.

If, on the other hand, it is decided in step S354 that the sampling datasatisfy the prerequisite judgment conditions, the main judgment isexecuted in step S355 and subsequent steps. As shown in FIG. 20, thenotch mark main judgment is executed over two stages in the embodiment,i.e., first judgment processing (step S355) and second judgmentprocessing (step S357) executed after the first judgment processing.

(First Notch Mark Judgment Processing)

First, the first judgment processing (step S355) is explained. In thefirst judgment processing, the sets of sampling data corresponding tothe detected notch mark candidate (hereafter may be referred to as “datagroup for the notch mark candidate”) are curvilinearly approximated andan error (offset) manifesting between the approximate curve and the datagroup for the notch mark candidate is judged.

The first judgment processing may be executed as follows. First,quadratic curvilinear (parabolic) approximation processing is executedon the data group for the detected notch mark candidate through, forinstance, the method of least squares. Such quadratic curvilinear(parabolic) approximation processing may be executed by, for instance,curvilinearly approximating the sampling data (x_(i), y_(i)),corresponding to the notch mark candidate and having been sampled at Nsampling points, through the method of least squares, as expressed inthe quadratic expression in (2-1) below.y=a ₀ +a ₁ x+a ₂ x ²  (2-1)

Through the method of least squares, the values for a₀, a₁ and a₂ aredetermined so as to achieve a minimal value in expression (2-2) below.S=(y ₁ −y)²+(y ₂ −y)²+ . . . +(y _(n) −y)²=(y ₁ −a ₀ −a ₁ x ₁ −a ₂ x ₁²)²+(y ₂ −a ₀ −a ₁ x ₂ −a ₂ x ₂ ²)² . . . +(y _(n) −a ₀ −a ₁ x _(n) −a ₂x _(n) ²)²  (2-2)

Since the values obtained by differentiating S expressed as in (2-2)above individually with a₀, a₁ and a₂ are invariably 0 at a minimalpoint, a₀, a₁ and a₂ that will achieve a minimal value for Sinexpression (2-2) can be determined, and then, a curvilinearapproximation expression can be determined as expressed in (2-1).

Once the approximate curve approximating the data group for the notchmark candidate is determined, the error manifesting between theapproximate curve and the data group for the notch mark candidate isascertained. For instance, approximate values are calculated based uponthe curvilinear approximation expression obtained through the method ofleast squares, as described above, each in correspondence to one of thesampling points at which the sampling data in the data groupcorresponding to the notch mark candidate have been sampled.

Next, the error manifesting between the approximate value data groupobtained as indicated in the curvilinear approximation expression andthe initial data group for the notch mark candidate is ascertained. Morespecifically, values each indicating the difference between the data ata given point in the approximate value data group obtained as indicatedin the curvilinear approximation expression and the data at thecorresponding sampling point in the initial data group for the notchmark candidate are calculated, and the average of these values iscalculated as the error between the approximate curve and the initialdata group. FIG. 23 presents a specific example of the approximate valuedata group obtained as indicated in the curvilinear approximationexpression and the initial data group for the notch mark candidate. Thesolid curve in FIG. 23 is the approximate curve, with “X” indicatingdata in the initial data group for the notch mark candidate and “O”indicating data in the approximate value data group obtained asindicated in the curvilinear approximation expression.

Then, a decision is made as to whether or not the error manifestingrelative to the approximate curve thus obtained satisfies a firstjudgment condition (error judgment). The first judgment condition basedupon which the error judgment is executed may be that the ratio of theerror relative to the depth (height) H of the notch mark candidateindicated by the approximate curve, as shown in FIG. 23, does not exceeda first judgment threshold value.

The depth (height) H of the notch mark candidate area indicated by theapproximate curve, as described above, may be calculated as thedifference between the largest value and the smallest value among theapproximate values calculated as indicated in the curvilinearapproximation expression. In other words, the first judgment conditionmay be that the ratio of the error manifesting between the approximatevalue data obtained as indicated in the curvilinear approximationexpression and the sampling data corresponding to the notch markcandidate, to the difference between the largest value and the smallestvalue among the approximate values calculated as indicated in thecurvilinear approximation expression does not exceed the first judgmentthreshold value (e.g., 1/10).

In the embodiment, the depth (height) H (e.g., the difference betweenthe largest value and the smallest value among the approximate valuescalculated as indicated in the curvilinear approximation expression) ofthe notch mark candidate indicated by the approximate curve is used asthe reference in the error judgment for the following reason.

Prior to the notch mark candidate judgment, the sinewave component inthe wafer edge shape data is canceled by folding back the sampling datacorresponding to the half cycle in the wafer edge shape data and thuscreating superimposed data (step S310 in FIG. 17). The resulting dataindicate a substantially flat waveform except for the area correspondingto the notch mark (see, for instance, FIG. 21). However, if the waferedge shape data contain saturated data, the waveform in the superimposeddata may become raised (shifted) over the saturated area. For thisreason, the notch mark candidate in the superimposed data may becomeshifted or may remain not shifted, depending upon the presence/absenceof saturated data, as shown in FIG. 24, resulting in fluctuation of thevalues indicated by the superimposed data over the notch mark candidatearea. For this reason, if approximate values calculated as indicated inthe curvilinear approximation expression are directly used as areference in the error judgment, the error judgment will be affected byany fluctuation of the data values in the notch mark candidate area.

Accordingly, instead of directly using the approximate values calculatedas indicated in the curvilinear approximation expression as a referencein the error judgment, the depth (height) H of the notch mark candidatearea indicated by the approximate curve, as shown in FIG. 24, is used asthe reference in the error judgment in the embodiment so as to ensurethat the error judgment can be executed without being affected by anyfluctuation of the values indicated in the superimposed data over thenotch mark candidate area.

It is desirable to select a value that will allow the data correspondingto the actual notch mark to be retained and will eliminate the datacorresponding to a noise area detected as a notch mark candidate, forthe first judgment threshold value. For instance, the results of errorjudgment tests executed to ascertain the extents of error is manifestingover the notch mark area and a noise area in data sampled from the waferedge shape data indicate that while the extent of error manifesting overthe notch mark area is equal to or less than 1/40 of the depth (height)H of the notch mark candidate area, the extent of error manifesting overthe noise area is equal to or greater than 7/10 of the depth (height) Hof the notch mark candidate area. This means that the first judgmentthreshold value should be, at least, within the range of 1/40 to 7/10 ofthe depth (height) H of the notch mark candidate area. Since the extentof error manifesting over the notch mark area is equal to or less than1/40 of the depth (height) H of the notch mark candidate area, it iseven more desirable to set the first judgment threshold value to 1/10 ofthe depth (height) H of the notch mark candidate area by allowing for acomfortable margin. The first judgment threshold value thus determinedshould be pre-stored into a first judgment threshold value storage areaat the storage means constituted with the memory or the like at thecontrol unit 180.

Through the first judgment processing described above, a notch markcandidate manifesting a greater error relative to the approximate curve,which is likely to be a noise area, is disqualified as a notch markcandidate. In addition, if the error between the notch mark candidateand the approximate curve is less than the first judgment thresholdvalue, the notch mark candidate area is more likely to be the actualnotch mark. Thus, by judging whether or not a notch mark candidate isthe actual notch mark through the first judgment processing describedabove, the judgment accuracy is improved. In addition, since any noiseareas detected as notch mark candidates are eliminated before the secondjudgment processing, the risk of erroneously judging a noise area to bethe notch mark in the second judgment processing is eliminated.

The first judgment processing described above is executed in step S355,and in step S356, a decision is made as to whether or not the errormanifesting between the sampling data corresponding to the notch markcandidate and the approximate curve satisfies the first judgmentcondition through the error judgment in the first judgment processing.

If it is decided in step S356 that the error does not satisfy the firstjudgment condition, the operation returns to step S351 to search foranother notch mark candidate, whereas the second judgment processing isexecuted in step S357 if the error is judged to satisfy the firstjudgment condition.

(Second Notch Mark Judgment Processing)

The second judgment processing (step S357) is now explained. In thesecond judgment processing, a decision is made as to whether or not acoefficient in the curvilinear approximation expression, representingthe curvilinear approximation of the sampling data corresponding to thenotch mark candidate, satisfies a second judgment condition. Throughthis judgment processing, it can be determined whether or not the shapeof the approximate curve corresponding to the notch mark candidate isclose to the shape of the actual notch mark (e.g., the shape of anapproximate curve obtained by curvilinearly approximating the samplingdata for the actual notch mark).

The second judgment processing may be executed as follows. If aquadratic curvilinear (parabolic) approximation processing has beenexecuted on the sampling data for the detected notch mark candidatethrough, for instance, the method of least squares, a decision is madeas to whether or not the coefficient a₂ of the quadratic term in thequadratic curvilinear expression in (2-1) is within an allowable rangeset as the second judgment condition.

It is desirable to set the allowable range to constitute the secondjudgment condition in correspondence to the actual shape of the notchmark formed at the wafer W, since the shape of the curve obtained bycurvilinearly approximating the data over the area of the notch markchanges depending upon the shape of the notch mark at the wafer W. Theallowable range constituting the second judgment condition may be setto, for instance, a reference value 30±18 if the notch mark is an actualnotch. The allowable range set as the second judgment condition asexplained above is pre-stored into an allowable range area at thestorage means constituted with the memory or the like at the controlunit 180.

Since a notch mark candidate with an approximate curve closer in shapeto the approximate curve of the actual notch mark is more likely to bethe actual notch mark, the notch mark judgment is executed with greateraccuracy through the second judgment processing.

In addition, since the second judgment processing is executed todetermine whether or not the shape of the approximate curvecorresponding to the notch mark candidate is close to the shape of theapproximate curve for the actual notch mark after ascertaining theextent of error manifesting between the approximate curve obtained bycurvilinearly approximating the notch mark candidate and the samplingdata corresponding to the notch mark candidate through the firstjudgment processing, the accuracy of the notch mark judgment is furtherimproved.

It is to be noted that while an explanation is given in reference to theembodiment on an example in which the main notch mark judgment isexecuted over two stages, i.e., the first judgment processing and thesecond judgment processing, the present invention is not limited to thisexample and the first judgment processing alone may be executed as themain notch mark judgment. Namely, the first judgment processing alonemay be executed as the main notch mark judgment to ensure that a noisearea over which deviant abnormal data such as saturated data manifest isnot erroneously judged to be the notch mark and thus, the accuracy ofthe notch mark judgment can be improved.

In addition, the second judgment processing alone may be executed as themain notch mark judgment in conjunction with a nontransparent wafersince problems attributable to saturated data which readily manifestwhen data are sampled from a transparent wafer, as described later, arenot a concern. In the case of a transparent wafer however, a pluralityof sets of saturated data are likely to manifest and, for this reason,if the second judgment processing alone is executed as the main notchmark judgment, a noise area may be erroneously judged to be the notchmark, depending upon how the saturated data are distributed.

For instance, let us assume that the second judgment processing alone isexecuted on sampling data containing saturated data such as those shownin FIG. 25. When wafer edge shape data corresponding to a noise areacontain a plurality of sets of saturated data manifesting discreetly, asshown in the figure, an approximate curve (quadratic curvilinearexpression) similar to the approximate curve for the actual notch markmay be obtained through quadratic curvilinear approximation by adoptingthe method of least squares, as shown in FIG. 26. In such a case, asignificant error (offset) between the approximate curve and thesampling data for the notch mark cannot be recognized through the secondjudgment processing and, as a result, a noise area may be erroneouslyjudged to be the notch mark provided that the coefficient a₂ for thequadratic term in the quadratic curvilinear expression is within theallowable range constituting the second judgment condition.

For this reason, it is desirable to execute the first judgmentprocessing prior to the second judgment processing, particularly inconjunction with a transparent wafer W. By judging the extent of theerror (offset) manifesting between the approximate curve and thesampling data for the notch mark in the first judgment processing, anyrandomness in the saturated data is not allowed to affect the notch markjudgment. Namely, since the error (offset) manifesting between theapproximate curve corresponding to a noise area where saturated datamanifest discretely, as shown in FIG. 26, and the sampling data for thenotch mark is significant enough to exceed the allowable range, such anoise area is disqualified as a notch mark candidate through the firstjudgment processing. As a result, a notch mark candidate undergoes thesubsequent second judgment processing only if the error (offset)manifesting between the corresponding approximate curve and the samplingdata for the notch mark is within the allowable range. In other words,the notch mark judgment can be executed without being affected by anysaturated data. As a result, a further improvement is achieved in thenotch mark judgment accuracy.

It is to be noted that similar problems to those inherent to atransparent wafer W may also occur with regard to a nontransparent waferW if abnormal data attributable to electrical noise or the likeoccurring in, for instance, the signal control manifest. For thisreason, the first judgment processing may be executed prior to thesecond judgment processing in conjunction with a nontransparent wafer Was well. In short, the same judgment processing may be executedregardless of the wafer type, i.e., whether data are being sampled froma transparent wafer W or a nontransparent wafer W.

The second judgment processing described above is executed in step S357,and a decision is made in step S358 as to whether or not the secondjudgment condition is satisfied, i.e., whether or not the coefficient a₂for the quadratic term in the curvilinear approximation expression forthe notch mark, e.g., a quadratic curvilinear expression, is within theallowable range set as the second judgment condition.

If it is decided in step S358 that the coefficient does not satisfy thesecond judgment condition, the operation returns to step S351 to searchfor another notch mark candidate, whereas if the coefficient is judgedto satisfy the second judgment condition, the operation returns to theprocessing in FIG. 17 to determine the notch mark candidate, having beenjudged to satisfy the judgment conditions in the notch mark judgmentprocessing, to be the actual notch mark in step S360.

Then, the operation returns to the processing in FIG. 7 to calculate theposition and the orientation of the notch mark in step S400. Forinstance, the position at which the sampling data corresponding to thenotch mark candidate having been judged to be the actual notch mark inthe notch mark judgment processing in FIG. 20 are present is designatedas the actual position of the notch mark in the wafer edge shape dataand the orientation of the notch mark is calculated.

Once the notch mark direction is calculated, the orientation of thewafer W is adjusted in step S500. For instance, based upon the positionand the orientation of the notch mark ascertained through the processingexecuted in step S400, the wafer W is set to achieve a specificorientation by rotating the rotary stage 210. The sequence of the waferpositioning processing thus ends. Subsequently, the wafer W is taken outof the positioning device 200 by, for instance, the common transfermechanism 160 which then carries it into a load-lock chamber or thelike. Thus, the wafer W, having been positioned (aligned) to achieve apredetermined orientation, is carried into the processing chamber.

(Another Structural Example of Substrate Transfer Device)

Next, another structural example that may be adopted in the substrateprocessing apparatus in an embodiment of the present invention isexplained in reference to a drawing. The present invention may beadopted in various other substrate processing apparatuses as well as inthe substrate processing apparatus 100 shown in FIG. 1. FIG. 27schematically illustrates the structure of a substrate processingapparatus that includes a multichamber vacuum processing unit.

The substrate processing apparatus 300 in FIG. 27 includes a vacuumprocessing unit 310 with a plurality of processing chambers 340 wheresubstrates such as wafers W undergo various types of processing such asfilm formation and etching and a transfer unit 120 that carries wafers Winto/out of the vacuum processing unit 310. Since the transfer unit 120adopts a structure substantially identical to that shown in FIG. 1, thesame reference numerals are assigned to components thereof withsubstantially identical functions and structural features to precludethe necessity for a repeated explanation thereof.

A common transfer mechanism (atmospheric pressure-side transfermechanism) 160 disposed inside the transfer chamber 130 at the transferunit 120 in FIG. 7 adopts a single arm structure that includes a singleend-effector. A base 162 at which the common transfer mechanism 160 islocked is slidably supported on a guide rail (not shown) extending overthe central area inside the transfer chamber 130 along the lengthwisedirection. A mover and a stator of a linear motor are respectivelydisposed at the base 162 and the guide rail. A linear motor drivemechanism (not shown) used to drive the linear motor is disposed at anend of the guide rail. The control unit 180 is connected to the linearmotor drive mechanism. Thus, the linear motor drive mechanism is drivenin response to a control signal provided by the control unit 180 to movethe common transfer mechanism 160 along the direction indicated by thearrow together with the base 162 on the guide rail.

FIG. 27 shows the vacuum processing unit 310 which includes, forinstance, six processing chambers 340A through 340F and is disposed at aside surface of the transfer unit 120. The vacuum processing unit 310includes a common transfer chamber 350 through which wafers are carriedinto/out of the six processing chambers 340A through 340F, with theprocessing chambers 340A through 340F disposed around the commontransfer chamber 350 respectively via gate valves 344A through 344F. Inaddition, first and second load-lock chambers 360M and 360N, which canbe evacuated, are connected respectively via gate valves 354M and 354Nwith the common transfer chamber 350. The first and second load-lockchambers 360M and 360N are connected at a side surface of the transferchamber 130 respectively via gate valves 364M and 364N.

As described above, the common transfer chamber 350 are connected withthe six processing chambers 340A through 340F and with the load-lockchambers 360M and 360N so as to open/close the passages between them asnecessary while sustaining a high level of airtightness in acluster-tool structure. In other words, communication with the spaceinside the common transfer chamber 350 is achieved as necessary. Inaddition, the passages between the transfer chamber 130 and the firstand second load-lock chambers 360M and 360N can be opened/closed asnecessary while sustaining a required level of airtightness.

A single type of processing or different types of processing can beexecuted on the wafers W in the processing chambers 340A through 340F.Stages 342A through 342F on which the wafers W are to be placed arerespectively disposed inside the processing chambers 340A through 340F.

The load-lock chambers 360M and 360N each have a function of temporarilyholding a wafer W to be transferred to the next stage after a pressureadjustment. The load-lock chambers 360M and 360N may include a coolingmechanism or a heating mechanism.

Inside the common transfer chamber 350, a transfer mechanism (vacuumpressure-side transfer mechanism) 370 constituted with an articulatedarm capable of extending/retracting, moving up/down and rotating, forinstance, is disposed. The transfer mechanism 370 is rotatably supportedat a base 372. The base 372 is allowed to slide freely over guide rails374 extending from the base end side toward the front end side insidethe common transfer chamber 350 via, for instance, an arm mechanism 376.

The load-lock chambers 360M and 360N and the processing chambers 340Athrough 340F can be accessed by the transfer mechanism 370 as it slidesalong the guide rails 374. For instance, to access the load-lock chamber360M or 360N or either of the processing chambers 340A and 340F locatedat positions facing opposite each other, the transfer mechanism 370 ispositioned on the guide rails 374 toward the base end of the commontransfer chamber 350.

To access any of the four processing chambers 340B through 340E, thetransfer mechanism 370 is positioned on the guide rails 374 toward thefront end of the common transfer chamber 350. Thus, all the chambersconnected to the common transfer chamber 350, i.e., the load-lockchambers 360M and 360N and the individual processing chambers 340Athrough 340F, can be accessed by the single transfer mechanism 370. Thetransfer mechanism 370 includes two end-effectors and thus is capable ofhandling two wafers W at a time.

It is to be noted that the transfer mechanism 370 may adopt a structureother than that described above, and may include, for instance, twotransfer mechanisms. Namely, a first transfer mechanism constituted withan articulated arm capable of extending/retracting, moving up/down androtating may be disposed toward the base end of the common transferchamber 350 and a second transfer mechanism constituted with anarticulated arm capable of extending/retracting, moving up/down androtating may be disposed toward the front end of the common transferchamber 350. In addition, the number of end-effectors at the transfermechanism 370 does not need to be two, and the transfer mechanism 370may include, for instance, a single end-effector, instead.

In the substrate processing apparatus 300 adopting the structure shownin FIG. 27, too, the positioning processing described earlier can beexecuted by engaging the positioning device 200 in operation. Thus, anoise area where abnormal data such as saturated data manifest is noterroneously judged to be the notch mark formed at the circumferentialedge of the substrate and the notch mark judgment accuracy is improvedin the substrate processing apparatus 300 as well.

It is to be noted that the number of processing chambers 340 in thesubstrate processing apparatus 300 does not need to be six, as shown inFIG. 27, and the substrate processing apparatus may include five orfewer processing chambers or it may include a greater number ofprocessing chambers. In addition, while the substrate processingapparatus in FIG. 27 includes a single vacuum processing unit 310constituted with a plurality of processing chambers connected around asingle common transfer chamber 350, the present invention may be adoptedin a substrate processing apparatus with a structure other than this.For instance, it may be adopted in a so-called tandem type substrateprocessing apparatus which includes two or more processing chamber unitseach made up with a plurality of processing chambers, connected around asingle common transfer chamber 350 via buffer chambers.

The wafer positioning processing in the embodiment described above maybe adopted in conjunction with a nontransparent wafer as well as atransparent wafer. For instance, abnormal data may be generated due todisturbance light or electrical noise when the detection target wafer isa nontransparent wafer, and in such a case, a noise area may beerroneously judged to be the notch mark formed at the wafer dependingupon how the abnormal data are distributed. For this reason, byexecuting the wafer positioning processing in the embodiment inconjunction with a nontransparent wafer, erroneous notch mark judgmentcan be prevented to improve the notch mark judgment accuracy.

While an explanation is given above on an example in which alight-transmitting sensor is used to detect the shape at the wafer edge,the present invention is not limited to this example and alight-reflecting sensor may instead be utilized to detect the shape ofthe wafer edge. Since light is allowed to be transmitted through almostthe entire area of a transparent wafer, there is a high likelihood ofthe light sensor generating saturated data (abnormal data) due to noiselight such as disturbance light, regardless of whether the light sensoris a light-transmitting sensor or a light-reflecting sensor. Thus, thereis a concern that depending upon how the saturated data are distributed,the noise area may be erroneously judged to be the notch mark at thewafer.

Accordingly, by executing the wafer positioning processing in theembodiments in conjunction with a light-reflecting sensor, sucherroneous notch mark judgment can be prevented and the notch markjudgment accuracy can be improved.

In addition, the wafer positioning processing in the embodiment may beexecuted in conjunction with a wafer at which an orientation flat isformed to be used as a notch mark, instead of a wafer at which an actualnotch is formed to be used as the notch mark.

Furthermore, it is obvious that the present invention may be achieved byproviding a system or an apparatus with a medium such as a storagemedium having stored therein a software program enabling the functionsof the embodiment and by reading out and executing the program stored inthe medium at the computer (or a CPU or MPU) of the system or theapparatus.

In such a case, the program itself read out from the medium such as astorage medium embodies the functions of the embodiment described aboveand the medium such as a storage medium having the program storedtherein embodies the present invention. The medium such as a storagemedium through which the program is provided may be, for instance, afloppy (registered trademark) disk, a hard disk, an optical disk, amagneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, aDVD-RW, a DVD+RW, magnetic tape, a nonvolatile memory card, or a ROM.Alternatively, such a program may be obtained through a download via anetwork.

It is to be noted that the scope of the present invention includes anapplication in which an OS or the like operating on the computerexecutes the actual processing in part or in whole in response to theinstructions in the program read out by the computer and the functionsof the embodiment are achieved through the processing thus executed, aswell as an application in which the functions of the embodiment areachieved as the computer executes the program it has read out.

The scope of the present invention further includes an application inwhich the program read out from the medium such as a storage medium isfirst written into a memory in a function expansion board loaded in thecomputer or a function expansion unit connected to the computer, a CPUor the like in the function expansion board or the function expansionunit executes the actual processing in part or in whole in response tothe instructions in the program and the functions of the embodimentdescribed above are achieved through the processing.

While the invention has been particularly shown and described withrespect to a preferred embodiment thereof by referring to the attacheddrawings, the present invention is not limited to this example and itwill be understood by those skilled in the art that various changes inform and detail may be made therein without departing from the spirit,scope and teaching of the invention.

1. A substrate positioning device that detects a notch mark formed at acircumferential edge of a substrate and positions said substrate basedupon said notch mark having been detected, comprising: a rotary stage onwhich said substrate is placed; a sensor unit that includes a lightsensor capable of detecting the circumferential edge of said substrateplaced on said rotary stage; and a control unit that obtains substrateedge shape data indicating detection values provided by said lightsensor of said sensor unit and positions said substrate based upon saidsubstrate edge shape data thus obtained, wherein: said control unitexecutes noise reduction processing for detecting sudden abnormal datain said substrate edge shape data obtained from said sensor uniteliminating said sudden abnormal data thus detected and interpolatingsaid substrate edge shape data by using estimated substrate edge shapedata generated based upon data from a surrounding area in place of theeliminated abnormal data, notch mark judgment processing by detecting anotch mark candidate in said substrate edge shape data having undergonesaid noise reduction processing and making a decision as to whether ornot an error manifesting between sets of data sampled over an areacorresponding to said notch mark candidate having been detected and anapproximate curve obtained by curvilinearly approximating the sets ofdata over the area corresponding to said notch mark candidate satisfiesa specific judgment condition and substrate positioning processing forpositioning said substrate based upon a notch mark satisfying saidspecific judgment condition, wherein: said specific judgment conditionupon which the decision is based in said notch mark judgment processingis that in reference to a height of said notch mark candidate arearepresented by said approximate curve, a ratio of the error to theheight of said notch mark candidate area does not exceed a predeterminedfirst judgment threshold value.
 2. A substrate positioning deviceaccording to claim 1, wherein: said predetermined first judgmentthreshold value is a value selected within a range of 1/40 to 7/10 ofthe height of said notch mark candidate area.
 3. A substrate positioningdevice according to claim 2, wherein: said predetermined first judgmentthreshold value is 1/10 of the height of said notch mark candidate area.4. A substrate positioning device that detects a notch mark formed at acircumferential edge of a substrate and positions said substrate basedupon said notch mark having been detected, comprising: a rotary stage onwhich said substrate is placed; a sensor unit that includes a lightsensor capable of detecting the circumferential edge of said substrateplaced on said rotary stage; and a control unit that obtains substrateedge shape data indicating detection values provided by said lightsensor of said sensor unit and positions said substrate based upon saidsubstrate edge shape data thus obtained, wherein: said control unitexecutes noise reduction processing for detecting sudden abnormal datain said substrate edge shape data obtained from said sensor uniteliminating said sudden abnormal data thus detected and interpolatingsaid substrate edge shape data by using estimated substrate edge shapedata generated based upon data from a surrounding area in place of theeliminated abnormal data, notch mark judgment processing by detecting anotch mark candidate in said substrate edge shape data having undergonesaid noise reduction processing and making a decision as to whether ornot an error manifesting between sets of data sampled over an areacorresponding to said notch mark candidate having been detected and anapproximate curve obtained by curvilinearly approximating the sets ofdata over the area corresponding to said notch mark candidate satisfiesa specific judgment condition and substrate positioning processing forpositioning said substrate based upon a notch mark satisfying saidspecific judgment condition, wherein: in said notch mark judgmentprocessing, superimposed substrate edge shape data are generated byoffsetting and superimposing data corresponding to a half cycle in saidsubstrate edge shape data having undergone said noise reductionprocessing and corresponding to one cycle of said substrate over thedata corresponding to the other half cycle and a notch mark candidate isdetected by using said superimposed data.
 5. A substrate positioningmethod for detecting a notch mark formed at a circumferential edge of asubstrate and positioning said substrate based upon said notch markhaving been detected, comprising: detecting the circumferential edge ofsaid substrate with a light sensor and obtaining detection valuesprovided by said light sensor as substrate edge shape data; detectingsudden abnormal data in said substrate edge shape data, eliminating thedetected sudden abnormal data and interpolating said substrate edgeshape data with estimated substrate edge shape data obtained based upondata from a surrounding area in place of the eliminated abnormal data;detecting a notch mark candidate in said substrate edge shape datahaving undergone said detecting sudden abnormal data in said substrateedge data, said eliminating the detected sudden abnormal data and saidinterpolating said substrate edge data and making a decision as towhether or not an error manifesting between sets of data sampled over anarea corresponding to the notch mark candidate having been detected andan approximate curve obtained by curvilinearly approximating the sets ofdata over the area corresponding to the notch mark candidate satisfies apredetermined judgment condition; and positioning said substrate basedupon a notch mark satisfying said predetermined judgment condition,wherein: said predetermined judgment condition upon which the decisionis based in said detecting a notch mark candidate is that in referenceto a height of said notch mark candidate area represented by saidapproximate curve, a ratio of the error to the height of said notch markcandidate area does not exceed a predetermined first judgment thresholdvalue.
 6. A substrate positioning method according to claim 5, wherein:said predetermined first judgment threshold value is a value selectedwithin a range of 1/40 to 7/10 of the height of said notch markcandidate area.
 7. A substrate positioning method according to claim 6,wherein: said predetermined first judgment threshold value is 1/10 ofthe height of said notch mark candidate area.
 8. A substrate positioningmethod for detecting a notch mark formed at a circumferential edge of asubstrate and positioning said substrate based upon said notch markhaving been detected, comprising: detecting the circumferential edge ofsaid substrate with a light sensor and obtaining detection valuesprovided by said light sensor as substrate edge shape data; detectingsudden abnormal data in said substrate edge shape data, eliminating thedetected sudden abnormal data and interpolating said substrate edgeshape data with estimated substrate edge shape data obtained based upondata from a surrounding area in place of the eliminated abnormal data;detecting a notch mark candidate in said substrate edge shape datahaving undergone said detecting sudden abnormal data in said substrateedge shape data, said eliminating the detected sudden abnormal data andsaid interpolating said substrate edge shape data and making a decisionas to whether or not an error manifesting between sets of data sampledover an area corresponding to the notch mark candidate having beendetected and an approximate curve obtained by curvilinearlyapproximating the sets of data over the area corresponding to the notchmark candidate satisfies a predetermined judgment condition; andpositioning said substrate based upon a notch mark satisfying saidpredetermined judgment condition, wherein: in said detecting a notchmark candidate, superimposed substrate edge shape data are generated byoffsetting and superimposing data corresponding to a half cycle in saidsubstrate edge shape data having undergone said detecting suddenabnormal data in said substrate edge shape data, said eliminating thedetected sudden abnormal data and said interpolating said substrate edgeshape data and corresponding to one cycle of said substrate over thedata corresponding to the other half cycle and a notch mark candidate isdetected by using said superimposed data.
 9. A computer readable storagemedium storing a computer program, the computer readable storage mediumbeing configured to execute the respective steps in claim
 5. 10. Acomputer readable storage medium storing a computer program, thecomputer readable storage medium being configured to execute therespective steps in claim 8.